HEY GUYS HEEELLLP!!!!

IM NEW TO THIS SITE, but check it out
i want to buy a 2008 mazda3 2.0 148 horsepower

i right away wanna put a GREDDY TURBO CHARGER 16G, Ex Housing: 8.0cm
HOWEVER I DONT KNOW ANYTHING ABOUT PSI CONVERSION HORSEPOWER

DO I NEED TO
purchase intercoolers, piping, blow-off valves separately in most cases AND IF SO WHAT ARE THE BEST AFTERMARKET USUALLY THE MOST EXPENSIVE? AND WHAT ABOUT THIS WASTE GATE DO I NEED THAT?